1. Field of the Invention
The present invention relates to a method for manufacturing a printed wiring board, in which a wiring pattern is formed using an inkjet process, and more particularly, to a method for manufacturing a printed wiring board, which can enhance the peel strength between an insulating layer and a conductive pattern by a two-step process, that is, a semi-hardening and full-hardening of the insulating layer.
2. Description of the Related Art
In the electronic devices, computers, communication devices, and so on, semiconductors or electronic components are mounted on a printed wiring board. Circuit patterns (conductive patterns) of the printed wiring board are highly densified by the miniaturization of the devices or high performance of the semiconductors.
Generally, the circuit patterns of the printed wiring board are formed using a subtractive process. In the subtractive process, the circuit patterns are formed using an electroless plating process, a patterning process, an electrolyte plating process, and an etching process. The subtractive process, however, is complex and presents a problem of having to dispose of waste liquid during the plating process or the etching process.
To solve this problem, techniques have been developed which form a conductive pattern and an insulating pattern on a surface of a substrate using an inkjet process. If the wiring pattern (insulating pattern/conductive pattern) is formed using the inkjet process, circuit width or pitch can be reduced and multi-layer architecture can be easily implemented. A method for forming the wiring pattern using the inkjet process is disclosed in Japanese Laid-Open Patent Publication Nos. 1999-163499 and 2005-210079.
According to Japanese Laid-Open Patent Publication No. 1999-163499, a printed wiring board is manufactured by simultaneously printing a conductive pattern and an insulating pattern, whose thickness is identical to that of the conductive pattern, on an insulating substrate using an inkjet process.
According to Japanese Laid-Open Patent Publication No. 2005-210079, an insulating pattern is formed an insulating substrate and a conducive pattern is then formed. Then, a multi-layered printed wiring board is manufactured by repeating the two steps. Specifically, the conductive pattern and the insulating pattern are printed on a polyimide film, and the insulating pattern is fully hardened by heating or infrared lamp. Then, the conductive pattern is formed on the hardened insulating pattern and is heated (fired).
The above-described conventional methods have a problem in that the peel strength between the insulating layer and the conductive layer is low because the conductive pattern is printed on the fully hardened insulating layer (insulating substrate or insulating pattern) and is fired, the peel strength between the insulating layer and the conductive layer is low.